RSS
Sam Noyoun posted an Instructable with 10 ways to improve your night vision. Robert Bruce Thompson and Barbara Fritchman Thompson covered some of these techniques in Astronomy Hacks (including the pirate eye patch trick), but there are a few I hadn't heard of:
1. Protect your night visionIt takes approximately 30 minutes for the human eye to adapt to darkness. Protect your night vision: do not look directly at bright objects (for instance car headlights when driving).
...
10 ways to improve your natural night vision - Link
Robert Bruce Thompson, who has had a lot of experience looking at dim objects in dark places, says that only a red filter will work: green and blue won't do the trick. Robert also says that the elite forces and soviet special forces techniques don't work.
Related:
Quite a bit of variance on the green versus red debate:
http://stlplaces.com/night_vision.html
http://www.astromax.org/activities/members/kniffen.htm
The logic of using blue-green is that since your eyes are most sensitive to it you can use considerably less total light reducing the total impact on your night vision.
The reasoning behind red is that the rods are relatively insensitive to the red and thus the light will have less impact.
Having spent too much time in photographic darkrooms with both red and green safelights (in the latter case I was working with red sensitive holographic film) My take is that keeping the apparent intensity at a minimum is more important than red or green.
Reply to this comment
Unfortunately, your take is mistaken. The rods, which give us our night vision, are pretty much unaffected by light 600nm or longer in wavelength, which is why astronomical LED flashlights use 620nm or longer LEDs. When you view a star chart with a red LED flashlight, you're viewing it with your cones. Your rods don't respond at all to the red light, leaving them available for viewing the faint fuzzies. Even a very bright red LED light shown directly into your eyes for a long time has essentially zero effect on your night vision. If you use light of a shorter wavelength, such as blue-green, your rods pick it up, even at very low illumination levels, and are desensitized.
The reason that a lot of military gear uses green light has nothing to do with preserving night vision. The WSO or whovever is looking at that green light has his night vision destroyed by it. The reason green light is used in this situation is that the human eye is most sensitive to green light, which allows the total brightness of the illumination to be as low as possible, making it more difficult for enemy observers to detect.
As to photographic darkrooms, I've also spent a long time working in them, for more than 40 years. Red safelights are used only with blue-sensitive and orthochromatic (sensitive to all colors except red) emulsions. For panchromatic emulsions, which are sensitive to any color of visible light, a green safelight again provides the maximum visibility at the minimum overall illumination level.
Reply to this comment